An 11-year-old girl presented with focal atrial tachycardia (AT) originating from inside the inferior vena cava (IVC). Sustained AT appeared 10 years after surgical repair of the congenital heart defects. Focal AT was successfully eliminated with radiofrequency application at the earliest activation site, about 8 mm below the IVC right atrium junction. These findings suggested the existence of an electrically continuous myocardial extension in the IVC and a real risk of AT originating from IVC late after cardiopulmonary bypass with IVC cannulation.